Agnor and University of Maryland astronomer Douglas Hamilton think they have figured out what the something was: Triton once had a companion, and when the ‘‘binary’’ neared Neptune, Neptune’s gravity broke the two apart, kept Triton and let the companion whirl off into space. Their results were reported in last week’s edition of the journal Nature. Agnor said in a telephone interview that an alternative ‘‘collision’’ model, in which a lone Triton would have crashed into another Neptune satellite, requires a chance encounter that would have been ‘‘geometrically unlikely’’. And an ‘‘aerodynamic drag’’ theory would need Neptune’s atmosphere to reach out and grab Triton and bring it into orbit. ‘‘But then the gas has to go away,’’ Agnor said, or Triton, like a spent satellite orbiting Earth, would lose so much speed it would fall into Neptune. In the binary model, Triton and its companion would have rotated around a gravitational point, or center of mass. As they approached Neptune, it pulled them apart to claim one of the companions—Triton—for its own. Binaries are common in the asteroid belt, and the planet Pluto actually forms a binary with its large moon, Charon. (LAT)

Hello, My Name Is . . .

When you introduce yourself to someone, your name does a good job of identifying you. No matter how you say your name, the person you’re addressing will know who you are. It’s the language, not the tone or timbre of your voice, that provides the identifying information. Bottlenose dolphins, researchers have discovered, have ‘‘names’’ as well. They aren’t words, of course, but distinctive whistles that contain identifying information. ‘‘We thought this was something fairly unique to human language,’’ said Vincent M. Janik of the University of St. Andrews in Scotland, the lead author of a paper on the subject in The Proceedings of the National Academy of Sciences. ‘‘Now we find it in dolphins, too.’’

Bottlenose dolphins have a fission-fusion social structure, in which groups break apart for periods and then get back together. Scientists have known since the 1960s that the dolphins make up distinctive whistles, or calls. ‘‘It’s always been suggested that they are important for staying in touch with each other,’’ Dr Janik said. The question for him and his colleagues was whether the whistles had unique identifying information or whether the dolphins were just responding to the tone of the sound or some other feature of it. To test this, they synthesized whistles, using real dolphin calls as a model. Each real whistle has a distinct pattern of frequency modulation, or the variation in frequency over time. The artificial whistles maintained these patterns, but eliminated other characteristics like harmonics, dynamics and extraneous noises (including the clicking sounds that the dolphins also make). Janik found that when the dolphins in a group were exposed to an artificial whistle modelled after that of a related group member, the dolphins turned toward the sound. To draw an analogy to humans, the frequency modulation pattern is the “language,” and the dolphins could identify it regardless of the whistle’s “voice.” Most other animals appear to rely on the sound of the voice, rather than any coded information, for recognition. (NYT)